Thanks FuryDan66. That gauge looks right in the middle (to me anyway), not working. Sometimes I've had issues with my 50 year old wiring harness and the battery was not charging. I could tool around town ok for a while, but as the new battery wore down,.... I had a similar crisis.
I then dropped a voltmeter across the battery and low and behold it was not charging. This is where I am coming from. If you measure the voltage you will know for sure, and having a voltmeter around is always a good thing to have in your (literal) tool box.
I'm sure you may know this, but here is what you do, just in case.
Set the meter to DC volts, with the car off and press one lead down on the positive side the other on the other side.
The voltage will be about 12V. Start the car and measure it again. It needs to go up. 13V, 13.5V or there abouts, is perfect.
If it doesn't go up, stays the same or less, something is wrong and it isn't your battery.
On the other hand, perhaps you just had a crappy battery, or sometimes a dead dead dead battery will wind up being unchargable and NFG.
But if you disconnected it after every use, it isn't going to drain through a short circuit/load in the car, since it is open-circuited.
If you re-attach the battery cable to the terminal and see small sparking going on, then you have a short somewhere in the car. Pull one fuse at a time until it no longer sparks to isolate the fault.
Alternator - Sometimes an alternator that is on its way out, will be intermittently bad. These can be hard to catch. If you see smoke pour out of your hood near the battery, it could be one of those flaky moments, where the internal regulator is being bad, overcharges the battery and boiling steam comes off, or the battery explodes. Most of the time though you will catch this happening.
Sorry for droning on, hope some of this helps.